Tuesday, February 20, 2018

Season 11 premier division, after RR2

Crosstable after RR2

Draw rate for the bookless part of the premier division is 34/56 (60.7%). This is quite low, the reason is that the bottom 2 engines lose many games. If we restrict to games in the top 5 the draw rate goes up to 17/20 (85%).

Stockfish, Komodo and Houdini are in the lead, Stockfish performed better against the weaker engines and it doesn't have a clear lead because of its loss to Komodo in RR1. At the bottom Fizbo and Ginkgo look like sure candidates for relegation. Andscacs is also losing games, but its wins over both Ginkgo and Fizbo give it a safety margin of 2 points above 7th place. Chiron and Fire are closer to the top with one loss each.

A few interesting games

Fire - Ginkgo: Ginkgo won a pawn after the opening, while Fire was ahead on eval. Fire temporarily gave a rook for a bishop defender, allowing it to attack the black king and later regain the material and be a up a pawn. Evals were at 1.5 when the game reached a rook ending with pawns on both flanks. The extra pawn was decisive and the engines' evals quickly jumped as they realized Fire was winning.

Stockfish - Ginkgo: Stockfish had an eval advantage of about 0.8 after the opening, with a bishop pair against Ginkgo's two knights. With less pieces on the board the bishops were very active and the evals increased. Stockfish traded down to a rook ending where all Ginkgo's pawns were isolated, an easy win.

Fizbo - Stockfish: After the opening both engines thought they were better. Stockfish created a pawn majority on the queen side, Fizbo countered by sacrificing a bishop for two pawns and creating an advanced passer on the queen side and another passer in the center. Stockfish won a pawn and took over the center. Fizbo traded a rook for a bishop and was a rook down, its two advanced passers were not enough compensation. The game ended with 3 queens on the board, Stockfish's material advantage was winning.

Ginkgo - Houdini: Evals were close to 0 after the opening. Ginkgo made an error on move 26 and allowed Houdini to put a strong bishop in the center. Houdini slowly gathered its forces on the queen side and then gave a pawn to open a file for the rooks to attack. Ginkgo had to defend its king, Houdini captured two pawns and this was enough for a win in a QRN vs QRB position.

Chiron - Ginkgo: Ginkgo had an small eval advantage for more than 30 moves, after a B for R trade. The game reached a RB vs RR position, and then Chiron's king side pawns started to advance and the evals turned to Chiron's favor. Ginkgo gave back the material but in the rook ending Chiron's passers were better and gave Chiron the win.

Houdini - Fizbo: Fizbo's king remained in the center without the option of castling. Houdini had mating threats on f7 and on the d file, Fizbo's defense collpased and the game was over after 26 moves.

Stockfish - Andscacs: Andscacs gave a rook for a bishop early in the game, Stockfish had an eval advantage of about 1 and increasing. By the time the game reached a R vs B ending Stockfish's eval was winning. Andscacs took longer to realize, without tablebases it continued to play a 6-man lost position for 30 moves until adjudication.

Fizbo - Ginkgo: Fizbo had an eval of 1 for a long time with the engines shuffling in a closed position. Fizbo opened the center, giving a pawn but ruining Ginkgo's pawn structure. Evals started to increase when Fizbo's king came forward, both engines had passers but Fizbo's passer was better protected and more advanced. The game was adjudicated in a RN vs RB position before Ginkgo lost a piece. A first win for Fizbo

Chiron - Fizbo: The game reached a QBN vs QBN position on move 29. Chiron had an eval advantage of over 1 as it went a pawn up, Fizbo tried to counter by sacrificing a bishop for pawns and exposing the white king. Fizbo's QN attacked but had to give Chiron a move after every 3 checks. In cycles of 3 moves Chiron created an advanced passer that Fizbo couldn't stop.

Stockfish - Komodo: Stockfish lost to Komodo in RR1 and the fans were hoping it could beat Komodo in RR2. Stockfish had a small eval advantage, the queen side and center were locked and the engines shuffled for a while. Komodo opened up the center and created a passer while giving Stockfish a pawn majority on the king side. The evals jumped to around 1 but fluctuated a lot as Komodo had possible perpetual check draws and Stockfish tried hard to avoid these. Stockfish gave a piece and tried to push a passer but could only achieve a draw.

Komodo had an eval advantage after the opening. Chiron
chose to give a pawn early and as compensation had more space and its pieces were better developed and active.

Komodo
defended patiently while the eval increased, 'a pawn is a pawn' as the saying goes. After a while Komodo's pieces were as strong as Chiron's, both engines battling to control the center.

The pieces slowly came off
the board and Komodo was still a pawn up and had better pawn structure. The
game reached a BN vs NN ending, with evals over 2.5.

The ending was slow and technical, when the white king moved forward Komodo created a passers in the center and Chiron couldn't stop it without losing material. This was the first loss for Chiron in the premier division.